Dry Heating of\nCurcumin in the Presence of Basic Salts\nYields Anti-inflammatory Dimerization Products

Curcumin exerts some of its biological effects via degradation\nproducts formed by spontaneous oxidation at physiological, i.e., weakly\nbasic, pH. Here, we analyzed products formed by dry heating of curcumin\nin the presence of a basic salt (sodium bicarbonate and others). Under\nthe dry heating conditions employed, curcumin was completely consumed,\nyielding products entirely different from those obtained by autoxidative\ndegradation in buffer. Bioassay-guided fractionation of the reaction\nmixture was used to identify and isolate compounds with anti-inflammatory\nactivity in a cell-based assay. This provided two dimers of curcumin,\ndicurmins A and B, featuring a partly saturated naphthalene core that\ninhibited lipopolysaccharide-induced activation of NF-κB in\nRAW264.7 cells. Dicurmin A and B are unusual derivatives of curcumin\nlacking key functional moieties yet exhibit increased anti-inflammatory\nactivity. The process of dry heating of polyphenols in the presence\nof a basic salt can serve as a novel approach to generating bioactive\ncompounds.